Definition
Plain language
A test where nothing happened — the thing being checked made no measurable difference.
As stated in the literature
An experimental condition producing no statistically or practically meaningful effect; valuable as a control when it rules out a competing explanation for an observed effect.
Also called: null results
Why it matters: Null results keep people from adopting defenses that only appear to work, and they rule out alternative explanations that would otherwise muddy a positive finding.
For example, a team tests whether adding a warning line to the system prompt reduces successful attacks and finds the attack rate is essentially unchanged.
Heard on the show
“That's not a power-limited null result.”Episode 020 — The Compliance Gap: Why AI Says Yes and Does No